Gear pump and motor

ABSTRACT

A gear pump and motor having a plurality of pumps and motors, each of which have at least three gears interengaged with one another, seal members disposed adjacent to the gears, and control means for selectively controlling the movement of the seal members toward or away from the gears of the pump and motors so as to selectively actuate the pumps and motors so as to attain a desired output.

United States Patent Motomura et al.

[ GEAR PUMP AND MOTOR [75] Inventors: Mitsuteru Motomura, Kamakura',

Masayuki Futamata, Tokyo; Kazuyuki Hirose, Yokohama; Kazuo Ban, Tokyo, all of Japan [73] Assignee: Kabushiki Kaisha Komatsu Seisakusho, Tokyo, Japan [22] Filed: July 10, 1973 21 Appl. No.: 377,965

[30] Foreign Application Priority Data July 11, 1972 Japan 47-68693 [52] US. Cl. 418/126, 418/196 [51] Int. Cl. F0lc 19/02, F030 3/00, F040 15/00 [58] Field of Search 418/125-129, 418/131, 133, 196; 417/283, 286, 310; 91/59 [56] References Cited UNITED STATES PATENTS 3,068,795 12/1962 Lauck 417/283 Mar. 25, 1975 3,427,985 2/1969 0111013 ..-118/12(w 3,597,131 8/1971 Schofield 418/126 Primary E.\'aminer-John .l. Vrablik Attorney, Agent, 01' Firm-Oblon, Fisher, Spivak, McClelland & Maier ABSTRACT A gear pump and motor having a plurality of pumps and m0t0rs,each of which have at least three gears interengaged with one another, seal members disposed adjacent to the gears, and control means for selectively controlling the movement of the seal members toward or away from the gears of the pump and motors so as to selectively actuate the pumps and motors so as to attain a desired output.

2 Claims, 19 Drawing Figures PATENTEDHARZSIBTS sum 01 [1F 17 r.p.m

Pump Drive Speed (/min) Gap (p) a 1 pl. mm.

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SHEET 06 HF 17 PATENTED 57.873252 SHEET 07UF 17 PATENTED MAR 2 5 I975 SHEET DBUF 17 mwJ mvm PATENTEU "AR25I975 sum 12 or 17 PATENIEB AR 2 5 I975 SHEET 13UF 17 SHEET -w-Il PATENTED MR2 PATENTED MR2 5 I975 SHEET lSUF 17 wow vow

PATENTED MR 2 5 5 SHEET lESUF 17 mow PATENTEBMAM 519. 5

SHEET 17UF 17 wov GEAR PUMP AND MOTOR BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a gear pump and motor, and more particularly to an improved gear pump and motor adapted for efficient operation at low speeds and having means for controlling the position ofa sealing member relative to the gears within the pump and motor.

2. Description of the Prior Art Conventional gear pumps and motors are generally of the pressure balance type which tend to improve the pump and motor efficiency by actuating the seal member to a position adjacent to the engaging area of the meshed gears by utilizing the discharge or supply pressure so as to prevent internal oil leakage from the sealing chamber formed by means of the gears and the seal member. The seal member utilized within the conventional gear pumps and motors is thus urged to perform the sealing function in response to the discharge or supply pressure of the oil, and consequently is always actuated in the biased direction. A common occurrence experienced with various construction and industrial machinery employing such gear pumps and motors of the pressure balance type is the reduction in the pumping efficiency and improper responsiveness of the hydraulic components during low speed operation of the drive source and seizure and wear of the seal and rotary members during high speed operation.

Furthermore, when the gear pump and motor is in the idle condition, wherein work is not provided, or the volume discharge of oil which is supplied is more than the required amount, as the pump hydraulic circuit always maintains a hydraulic resistance of approximately lO-l5kg/cm such operation results in the consumption of some required power, and yet the discharged hydraulic oil is merely circulating throughout the pump and oil tank. Such operation, however merely consumes power and further increases the temperature of the oil with the result that such is not desirable for either the pump or the conduits and actuators within the hydraulic circuit for the increase in the oil temperature reduces the viscosity of the oil, and accordingly, such results in the decrease of the sealing effect of the seal members whereupon an increase in the internal oil leakage will occur which in turn causes oil leakage within the circuit conduits and actuators. In order to prevent such disadvantages, it is usually necessary to enlarge the conduits and valves so as to reduce the fluid resistance, however, in order to enlarge the valves and conduits, it sometimes becomes difficult to mount the same upon a vehicle, and in addition, it usually is not economical to do so.

The conventional gear pumps and motors have been generally used heretofore for transmission pumps, brake pumps, steering pumps, actuator pumps, or the like, but with respect to the operation of transmission pumps, brake pumps, and steering pumps, such pumps are required to perform their functions even during the idling operation of the engine which is used as a drive source ofthe pump. However, as the volume efficiency of the pumps of this type is generally reduced when the rotational speed is decreased, and particularly when the oil temperature is high, the volume efficiency may become 50% or less, the idling speed of the engine of the construction machinery being approximately 500 600 rpm. Under such conditions, even simple operations are difficult to perform often or coordinate.

In order to counteract such disadvantages, the speed of the drive source must be increased. or a pump having a larger volume discharge must be preselected. However, such requirements can be inconvenient. and the power loss noted heretofore is not resolved. If a pump having a sufficient capacity for supplying enough oil even during low speed operation of the engine is adopted, it has been noted that excessive torque is produced, and excessive volume discharge must be released through means of a relief valve during high speed operation thereof which of course is not preferable.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved gear pump and motor which may efficiently control the hydraulic fluid volume dis charge in response to the load.

Another object of the present invention is to provide an improved gear pump and motor which has a plurality of pumps and motors capable of being selectively driven or stopped in response to the load.

Still another object of the present invention is to provide an improved gear pump and motor which may prevent a substantial temperature increase of the hydraulic fluid and which may restrict the power loss of the prime mover for the gear pump and motor by controlling the discharge pressure and volume of the fluid, the rota tional speed of the pump and motor, and the external force applied thereto.

Yet another object of the present invention is to pro vide an improved gear pump and motor which may sufficiently compensate for the conventional reduction in volume efficiency during low speed operation of the drive source for the pump and motor, and the wear of the seal member and other pump components due to long periods of usage during high speed operation.

A further object of the present invention is to provide an improved gear pump and motor in which the degree of sealing between the gears and the seal member may be selected at an optimum value so as to prevent the wear and seizure of the seal member by the rotary components during high speed operation.

BRIEF DESCRIPTION OF THE DRAWINGS Various other objects, features, and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the several views, and wherein:

FIG. 1 is a graph showing the relationship between the volume efficiency and pump drive speed of a conventional gear pump and motor;

FIG. 2 is a graph showing the relationship between the fluid leakage and seal gap of a conventional gear pump and motor;

FIG. 3 is a schematic view, partly in section, of one embodiment ofa gear pump and motor constructed according to the present invention and showing its cooperative parts;

FIG. 4 is a view similar to that of FIG. 3, showing however the gear pump and motor under high speed operative conditions;

FIG. 5 is another embodiment of a control valve which may be utilized within the gear pump and motor shown in FIGS. 3 and 4;

FIG. 6 is a view similar to that of FIG. 3 showing however another embodiment of a gear pump and motor constructed according to the present invention and showing it cooperative parts;

FIG. 7 is a view similar to that of FIG. 6, showing however the gear pump and motor under high speed operative conditions;

FIG. 8 is a view similar to that of FIG. 3 showing however still another embodiment of a gear pump and motor constructed according to the present invention and showing its cooperative parts;

FIG. 9 is a partial, cross-sectional view of the gear pump and motor of FIG. 8 taken along the line IXIX in FIG. 8;

FIG. 10 is a view similar to that of FIG. 8, showing however the gear pump and motor under high speed operative conditions;

FIG. 11 is a view similar to that of FIG. 3 showing however yet another embodiment of a gear pump and motor constructed according to the present invention and showing its cooperative parts;

FIGS. 12 and 13 are views similar to that of FIG. 11, showing however the gear pump and motor under various operative conditions whereby the output torque and speed may be varied;

FIG. 14 is a schematic view of a further embodiment of a gear pump and motor constructed according to the present invention and showing its cooperative parts;

FIG. 15 is a view similar to that of FIG. 14, showing however the gear pump and motor under high speed operative conditions;

FIG. 16 is a view similar to that of FIG. 14 showing however a still further embodiment of a gear pump and motor constructed according to the present invention and showing its cooperative parts, the gear pump and motor being under high speed operative conditions;

FIG. 17 is a view similar to that of FIG. 16 showing however the gear pump and motor under low speed operative conditions;

FIG. 18 is a view similar to that of FIG. 14 showing however a still further embodiment ofa gear pump and motor constructed according to the present invention and showing its cooperative parts, the gear pump and motor being under high speed operative conditions; and

FIG. 19 is a view similar to that of FIG. 18 showing however the gear pump and motor under low speed operative conditions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to better understand the gear pump and motor of the present invention, the characteristics of a conventional gear pump and motor will first be described with particular reference to FIGS. 1 and 2, which are performance graphs respectively illustrating the relationship between the pump drive speed and the volume efficiency, and the relationship between the seal gap and the amount of fluid leakage.

Conventional gear pumps and motors are usually of the pressure balance type which have a seal member within the vicinity of the area in which the gears engage, and which is urged toward the gears by utilization of the discharge or supply pressure so as to prevent oil from leaking from the sealing chamber formed by means of the seal member and the gears. When such conventional gear pumps and motors are utilized particularly in conjunction with various construction machinery, the efficiency'of such gear pumps and motors is reduced during low speed operation of the engine with the result that the response of the various hydraulic components and devices is also reduced. In addition. when the engine is operated at high speeds. the seal member readily becomes seized or worn by the rotary members.

As noted heretofore. the conventional gear pumps and motors of the pressure balance type operate such that when the drive speed is decreased. the volume efficiency is also decreased as shown in FIG. I, and when the temperature of the hydraulic oil increases, the volume efficiency is reduced still further with the result that the volume efficiency is sometimes reduced to a value approximately 50%. Construction machinery such as for example, tractors and bulldozers. ordinarily utilize idling engine speeds of approximately 500 600 rpm, and in order to compensate for the reduced responsiveness of the hydraulic components and devices, such as for example, the transmission pump. brake pump, steering pump, or working pump. during low speed operation of the engine, the idling speed of the engine is ordinarily raised or the output capacity of the hydraulic devices is ordinarily increased, but these techniques merely serve to increase the power loss.

Furthermore, the amount of internal hydraulic leakage from the seal gap between the seal member and the gears is generally proportional to the cube of the gap, and has the tendency shown in FIG. 2 wherein curve a illustrates the amount of leakage from the gap between the end portions of the gear teeth and the seal block, curve b represents the amount of leakage from the gap between the side surfaces of the gears and the sides of the seal member. and curve 0 illustrates the amount of leakage from the gap between the seal block and the sides of the seal member.

The gear pump and motor of the present invention seeks to control the actuation of the seal member by means of the discharge pressure, the discharge flow rate, the rotational speed of the pump. or by an external force, so as to effectively control the pump discharge and pressure whereby the temperature of the hydraulic oil will be prevented from appreciably rising, and the volume efficiency will be substantially improved, and wear of the pump components will be reduced.

Reference is now made to FIG. 3 in which there is shown a first embodiment of the gear pump and motor constructed according to the present invention as including a housing 1 in which a drive gear 3, driven by a prime mover, not shown, and driven gears 4 and 5 intermeshed with the drive gear 3, are respectively, rotatably supported. Laterally extending intake ports 7 and 8, and exhaust ports 10 and 11, are provided within the walls of the housing 1, and a seal block B1 is disposed within the vicinity of the engaging area S1 between the drive gear 3 and the driven gear 4 so as to form with housing 1 and gears 3 and 4, a first pump and motor, generally indicated by the reference character P]. A seal block B2 is likewise provided within the vicinity of the engaging area S2 between the drive gear 3 and the driven gear 5 so as to similarly form a pump and motor, generally indicated by the reference character P2. 

1. A gear motor comprising: a housing; first, second and third gears disposed within said housing; first and second seal blocks disposed upon opposite sides of the engaging area between said first and second gears; third and fourth seal blocks disposed upon opposite sides of the engaging area between said second and third gears; first, second, third and fourth openings in the housing associated with the first, second, third and fourth seal blocks, respectively, which openings selectively function as inlets and outlets to the motor, at least four cylinders respectively mounted upon said housing relative to said four seal blocks; at least four piston means respectively slidably disposed within said four cylinders for actuating said four seal blocks; control valve means for selectively actuating said piston means having first, second, third and fourth ports at one side thereof and fifth and sixth ports at the other side thereof; and spool means movable within said valve means between a first position at which said first and second ports are in communication with said fifth port and said third and fourth ports are in communication with said sixth port, and a second position at which said first port is in communication with said fifth port, said second port is in communication with said third port, and said fourth port is in communication with said sixth port, for selectively delivering hydraulic fluid from an external source to two of the four openings associated with said four seal blocks and for exhausting from the other two of said four openings and also for delivering hydraulic fluid to two of said four cylinders when said spool means is in said first position, and for delivering hydraulic fluid to one of the four openings associated with the four seal blocks and for exhausting from another one of said four openings and also delivering hydraulic fluid to one of said four cylinders when said spool means is in said second position, for respectively urging said pistons and said seal blocks toward said three gears for generating various torques therefrom.
 2. A gear motor as set forth in claim 1, further comprising: a manually operable directional control valve having first and second apertures at one side thereof and third and fourth apertures At the other side thereof; and a spool movable between a neutral position at which said first and second apertures are not connected to any other aperture and in which said third aperture is in communication with said fourth aperture, a first operative position at which said first aperture is in communication with said third aperture and said second aperture is in communication with said fourth aperture, and a second operative position at which said first aperture is in communication with said fourth aperture and said second aperture is in communication with said third aperture for selectively reversing the direction of the hydraulic fluid flow by shifting said spool between said positions. 